The present invention relates to balloon catheters and, more particularly, to a non-shortening wrapped balloon configured to expand with essential radial symmetry to a predetermined diameter upon application of a predetermined pressure thereto.
Balloon catheters are well known in the art. Such catheters are employed in a variety of medical procedures, including dilation of narrowed blood vessels, placement of stents and other implants, and temporary occlusion of blood vessels.
In a typical application, the balloon is advanced to the desired location in the vascular system. The balloon is then pressure-expanded in accordance with a medical procedure. Thereafter, the pressure is removed from the balloon, allowing the balloon to contract and permit removal of the catheter. The balloon must be formed of a material which has a low profile to allow entry through a vessel, yet is readily pressure-expanded and able to contract upon removal of the inflation pressure.
Procedures such as these are generally considered minimally invasive, and are often performed in a manner which minimizes disruption to the patient's body. As a result, catheters are often inserted from a location remote from the region to be treated. However, previous wrapped balloons have suffered from problems such as overexpansion during inflation and shortening of the balloon due to inflation resulting in unreliable placement of the balloon in a vessel. This is particularly concerning when large diameter balloon are employed in medical procedures because the maximum hoop stress of the inflated balloon material can more easily be exceeded causing the balloon to rupture or burst.
Previous attempts to compensate for overexpansion have been made.
However, only the present invention provides a non-shortening balloon that expands to a maximum diameter in an essentially radial symmetric fashion. While an advantage of a low angle wrapped balloon is that the wrap is accomplished at the deflated diameter making mounting to a catheter shaft possible. The balloon then inflates to a larger diameter in use at which time the wrap angle rotates to the neutral angle. A typical low angle wrapped balloon will foreshorten as it is expanded. Compensation for foreshortening by means of accordion-scrunching-length-storage is limited in that the longitudinal folds push out and then the angle moves to the neutral angle thus the foreshortening is not eliminated during inflation. The devices and methods of the present invention minimize foreshortening while maintaining an essentially radial inflating balloon, and allow the balloon to be mounted on a smaller diameter catheter shaft. The present invention solves the clinical issues of accurate placement of a balloon or stent due to foreshortening of traditional wrapped balloons. The present invention also prevents undue trauma on vessel endothelial layers and possibility of plaque fragmentation caused by inflation movement of asymmetric inflating balloons.